Tomorrow’s memorial service for Michael Jackson will be a time to celebrate his achievements and forget his failings — including his rumoured addiction to the opiate painkiller pethidine (Demerol). Being hooked on prescribed painkillers may conjure up a more benign image than abusing heroin, but pharmacologically they are much the same. And Jackson’s plight is bound to reinforce the myth and prejudice that surrounds the opiate family.

When used properly, opiates such as morphine, diamorphine (heroin) and pethidine are neither dangerous nor addictive and remain one of the most useful weapons in a doctor’s armoury. “Among the remedies which it has pleased Almighty God to give to man to relieve his sufferings, none is so universal and so efficacious as opium.” So wrote the physician Thomas Sydenham in 1680, and given the major strides in medicine since then, it is a credit to the opium family that his words still hold true.

Opium is the dried extract of opium poppy seed-heads and has been used for millennia to ease pain and discomfort. The active ingredients are opium alkaloids, and morphine — named after Morpheus, the god of sleep — was the first to be isolated in 1806.

Since then, other natural components, including codeine, have been identified and pharmacologists have gone on to manufacture synthetic versions such as pethidine (best known for its use during childbirth).

All the alkaloids have slightly differing properties but their basic mode of action remains the same in that they mimic naturally occurring painkilling chemicals — encephalins, endorphins and dynorphins — found in the brain. And besides their potent painkilling properties, opiates also induce a sense of euphoria and detachment and have a powerful calming effect.

But, as with all drugs, there is a downside. Opiates also suppress the parts of the brain that control wakefulness, breathing and coughing, while stimulating the centre responsible for nausea and vomiting: a double-whammy that makes overdose lethal. If loss of consciousness and impaired breathing doesn’t lead to respiratory and cardiac arrest, then the combination of vomiting and a blunted cough reflex mean that the victim can choke to death.

Lethal overdose is a real risk in anyone injecting the drug intravenously (IV). The onset of influence is much more rapid, and the effect more profound, than slower routes of administration such as taking it by mouth or injecting under the skin or into a muscle — one reason why IV injections are rarely used outside of a hospital.

The risk is further compounded by the fact that illegal drug users often have no way of being sure of the dose. Suppliers cut their product with so many agents that the strength can vary tremendously from dealer to dealer, and users play Russian roulette each time they shoot up.

Intravenous injection of the pharmaceutical-grade opiates, where the dose can be calculated down to fractions of a milligram, is generally very safe and can provide rapid relief in situations such as heart attack, broken bones and after surgery. And in the unlikely event of a reaction, doctors can administer an antidote (naloxone) that can reverse the effects of opiates within minutes.

We will have to wait for the results of the post-mortem examination to know what killed Michael Jackson, but speculation has centred on the fact that he suffererd a cardiac arrest shortly after being given an injection of pethidine (or possibly the anaesthetic agent propofol). There is no medical justification for giving intravenous opiates in the circumstances leading up to Jackson’s demise, and propofol should only ever be used by an anaesthetist. Either could have caused his heart to stop. But it is not the risk of overdose that concerns most patients. In my experience they tend to be far more concerned about the risk of addiction, and the implication that being put on morphine means that they have been written off by their doctors — both unfounded fears.

One of the great paradoxes in pain management is that addiction is unusual when opiates such as morphine are used appropriately. If you are prescribed a painkiller because you are in pain, you are unlikely to have problems coming off it when you no longer need it. But if you take the drug purely for its euphoric effects then the risk of addiction is very high, and can develop within days.

If the drug is suddenly stopped (usually because the user runs out of money), there will be a range of unpleasant withdrawal effects, which typically include restlessness, twitching, a runny nose, goosebumps, abdominal pain, vomiting and diarrhoea — so-called “cold turkey” and one of the principle drivers for searching out the next hit.

The stigma surrounding the use of opiates is another problem, and one that doctors, particularly those working in the field of cancer, have been battling for years. While high doses may hasten death in a very poorly patient who is nearing the end of his or her life, the drugs themselves have no impact on life expectancy in other patients. Contrary to common perception opiates are generally used to ease pain and suffering and allow people to get on with their lives, rather than to confine them to bed in a drug-induced haze.

It has been suggested that Jackson developed an opiate habit after he was prescribed pethidine to ease the pain of burns sustained during an accident in the late Eighties. At first glance this may appear to undermine the idea that appropriate use tends not to lead to addiction, but it is questionable whether he did use it appropriately – particularly in the latter years. The pethidine may have been prescribed, but by what sort of doctor?

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